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<div class="section" id="boost-mpl-aux-lambda-support">
<h1><a class="toc-backref" href="./broken-compiler-workarounds.html#id1609">BOOST_MPL_AUX_LAMBDA_SUPPORT</a></h1>
<div class="section" id="id1384">
<h3><a class="subsection-title" href="#synopsis" name="synopsis">Synopsis</a></h3>
<pre class="literal-block">
#define <a href="./aux-lambda-support.html" class="identifier">BOOST_MPL_AUX_LAMBDA_SUPPORT</a>(arity, fun, params) \
    <em>unspecified token sequence</em> \
/**/
</pre>
</div>
<div class="section" id="id1385">
<h3><a class="subsection-title" href="#description" name="description">Description</a></h3>
<p>Enables metafunction <tt class="literal"><span class="pre">fun</span></tt> for the use in <a class="reference internal" href="./lambda-expression.html">Lambda Expression</a>s on
compilers that don't support partial template specialization or/and
template template parameters. Expands to nothing on conforming compilers.</p>
</div>
<div class="section" id="id1386">
<h3><a class="subsection-title" href="#header" name="header">Header</a></h3>
<pre class="literal-block">
#include &lt;<a href="../../../../boost/mpl/aux_/lambda_support.hpp" class="header">boost/mpl/aux_/lambda_support.hpp</a>&gt;
</pre>
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<div class="section" id="id1387">
<h3><a class="subsection-title" href="#parameters" name="parameters">Parameters</a></h3>
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<col width="32%" />
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<tr><th class="head">Parameter</th>
<th class="head">Requirement</th>
<th class="head">Description</th>
</tr>
</thead>
<tbody valign="top">
<tr><td><tt class="literal"><span class="pre">arity</span></tt></td>
<td>An integral constant</td>
<td>The metafunction's arity, i.e. the number of its
template parameters, including the defaults.</td>
</tr>
<tr><td><tt class="literal"><span class="pre">fun</span></tt></td>
<td>A legal identifier token</td>
<td>The metafunction's name.</td>
</tr>
<tr><td><tt class="literal"><span class="pre">params</span></tt></td>
<td>A <a class="reference external" href="http://www.boost.org/libs/preprocessor/doc/data/tuples.html" target="_top">PP-tuple</a></td>
<td>A tuple of the metafunction's parameter names, in
their original order, including the defaults.</td>
</tr>
</tbody>
</table>
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<div class="section" id="id1388">
<h3><a class="subsection-title" href="#expression-semantics" name="expression-semantics">Expression semantics</a></h3>
<p>For any integral constant <tt class="literal"><span class="pre">n</span></tt>, a <a class="reference internal" href="./metafunction.html">Metafunction</a> <tt class="literal"><span class="pre">fun</span></tt>, and arbitrary types <tt class="literal"><span class="pre">A1</span></tt>,... <tt class="literal"><span class="pre">An</span></tt>:</p>
<pre class="literal-block">
template&lt; typename A1,<em>...</em> typename A<em>n</em> &gt; struct fun
{
    // <em>...</em>

    <a href="./aux-lambda-support.html" class="identifier">BOOST_MPL_AUX_LAMBDA_SUPPORT</a>(n, fun, (A1,<em>...</em>A<em>n</em>))
};
</pre>
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<tbody valign="top">
<tr class="field"><th class="field-name">Precondition:</th><td class="field-body">Appears in <tt class="literal"><span class="pre">fun</span></tt>'s scope, immediately followed by the scope-closing
bracket (<tt class="literal"><span class="pre">}</span></tt>).</td>
</tr>
<tr class="field"><th class="field-name">Return type:</th><td class="field-body">None.</td>
</tr>
<tr class="field"><th class="field-name">Semantics:</th><td class="field-body">Expands to nothing and has no effect on conforming compilers. On compilers that
don't support partial template specialization or/and template template parameters
expands to an unspecified token sequence enabling <tt class="literal"><span class="pre">fun</span></tt> to participate in
<a class="reference internal" href="./lambda-expression.html">Lambda Expression</a>s with the semantics described in this manual.</td>
</tr>
</tbody>
</table>
</div>
<div class="section" id="id1389">
<h3><a class="subsection-title" href="#example" name="example">Example</a></h3>
<pre class="literal-block">
template&lt; typename T, typename U = int &gt; struct f
{
    typedef T type[sizeof(U)];

    <a href="./aux-lambda-support.html" class="identifier">BOOST_MPL_AUX_LAMBDA_SUPPORT</a>(2, f, (T,U))
};

typedef <a href="./apply.html" class="identifier">apply</a><tt class="literal"><span class="pre">1</span></tt>&lt; f&lt;char,<a href="./placeholders.html" class="identifier">_1</a>&gt;,long &gt;::type r;
<a href="./assert.html" class="identifier">BOOST_MPL_ASSERT</a>(( is_same&lt; r, char[sizeof(long)] > ));
</pre>
</div>
<div class="section" id="id1390">
<h3><a class="subsection-title" href="#see-also" name="see-also">See also</a></h3>
<p><a class="reference internal" href="./macros.html">Macros</a>, <a class="reference internal" href="./metafunctions.html">Metafunctions</a>, <a class="reference internal" href="./lambda-expression.html">Lambda Expression</a></p>
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